Device for detecting the position of a railway vehicle on a track

ABSTRACT

A device for detecting the position of a train on a railway track equipped with a centralized control over the travel of the train using a transmission cable having crossings or other means defining periodic phase inversions of the magnetic field of the cable. It comprises three antennas located underneath the floor of the locomotive of the train and aligned one after the other in the longitudinal direction of the track, a band-pass filter connected to each antenna, three phase detectors, each one having two inputs connected to the outputs of two of the band-pass filters in accordance with the three different possibilities, such phase detectors being arranged to deliver an output signal only when their input voltages are in phase opposition, a logic circuit having three inputs connected respectively to the outputs of the three phase detectors for detecting the direction of travel of the train, and a summing circuit for totalizing the number of marking points crossed by the train connected to the outputs of the logic circuit, such logic circuit having two outputs delivering counting and deduction signals to the summing circuit.

United States Patent [72] Inventors Christian Jauquet Charleroi; JosephClaes, Serclaes de Tilly, both of Belgium [21] Appl. No. 853,346 [22]Filed Aug. 27, 1969 [45] Patented Sept. 28, 1971 [73] Assignee Ateliersde Constructions Electriques de Charleroi (ACEC) Charleroi, Belgium [32] Priority Aug. 30, 1968 3 3 Belgium [3 l 1 62,837

[54] DEVICE FOR DETECTING THE POSITION OF A RAILWAY VEHICLE ON A TRACK 2Claims, 3 Drawing Figs.

[52] U.S. Cl 340/23, 246/187 B, 180/98 [51] Int. Cl G08g1/00 50] Fieldof Search 340/23; 180/98; 246/187 B [5 6] References Cited UNITED STATESPATENTS 3,029,893 4/1962 Mountjoy 246/187 B 3,440,600 4/1969 Frech et al340/23 FOREIGN PATENTS 1/1969 Germany OTHER REFERENCES Primary Examiner-Kathleen H. Claffy Assistant Examiner-Jan S. Black Attorney-Raymond A.Robic ABSTRACT: A device for detecting the position ofa train on arailway track equipped with a centralized control over the travel of thetrain using a transmission cable having crossings or other meansdefining periodic phase inversions of the magnetic field of the cable.It comprises three antennas located underneath the floor of thelocomotive of the train and aligned one after the other in thelongitudinal direction of the track, a band-pass filter connected toeach antenna, three phase detectors, each one having two inputsconnected to the outputs of two of the band-pass filters in accordancewith the three different possibilities, such phase detectors beingarranged to deliver an output signal only when their input voltages arein phase opposition, a logic circuit having three inputs connectedrespectively to the outputs of the three phase detectors for detectingthe direction of travel of the train, and a summing circuit fortotalizing the number of marking points crossed by the train connectedto the outputs of the logic circuit, such logic circuit having twooutputs delivering counting and deduction signals to the summingcircuit.

PATENTED SE 2 8 |97| Fig.1

Fig.3

II-VVI'INTUR-SI' Christian JAUQUET Joseph CLAES ATTORNEY DEVICE FORDETECTING THE POSITION OF A RAILWAY VEHICLE ON A TRACK This inventionrelates to an apparatus for establishing a twoway communication betweena central location and a train or any other railway vehicle by inductionbetween a cable forming a loop located between the rails on which therailway vehicle travels, and receiving and transmitting antennas locatedon the locomotive of the railway vehicle.

In order to know the position of a train in a sector defined by theabove-mentioned cable, it is know to give marking points to such cablein such a way that regularly spaced crossings are detected by thelocomotive, taking advantage of the fact that, at the passage of suchmarking points, the signals received by the antennas undergo either avariation of amplitude or an inversion of phase. The marking points maythen be counted, which provides an indication of the position of thetrain in the sector.

The detection by amplitude variations presents serious drawbacksconcerning the security thereof, more particularly when the markingpoints consist of simple crossings wherein the time interval duringwhich the lowering of the level of the signals received occurs in veryshort. A stray signal occuring at the passage of a crossing may resultin the nondetection of such crossing and the train will, in this case,be located closer to the next obstacle that it is supposed to be.

The detection by phase inversion is much safer. Indeed, because at leasttwo antennas are always used on the locomotive, to ensure the continuityof the transmission at the passage of a crossing and because thedistance between these two antennas, in the direction of movement, isapproximately 2 meters, the time interval, for a train travelling at 200km./h., during which the phase difference of 180 exists between thevoltages detected by the two antennas is in the order of 36milliseconds. This provided a signal which may be more easilydistinguished from a stray signal.

The present invention more specially concerns apparatuses where use inmade of the last-mentioned detection process, and ascertains the measureof the position of the trains against interfering stray signals.

It may happen that a train, stopped in a sector defined by a cablestarts to go backwards, either accidentally in a hill or to carry out ashunting operation, or for any other reason. In this case, it isimportant that the marking points encountered when going backward be notcounted the same way as if they were crossed in the normal direction oftravel, but they may be deducted. Otherwise, upon resuming the normaltravelling direction, these marking points would have been counted threetimes instead of one, which would obviously falsify the indication ofthe position of the train.

The invention provides for the deduction of the marking pointsencountered when going backward whatever may be the direction of travelof the train on the tracks. It comprises, to that effect, means fordetecting the incoming of the locomotive in the sector defined by thecable either by one or the other of its driving positions.

The device, in accordance with the invention, is applicable to anapparatus in which use is made of a transmission cable having crossingsor other means defining periodic phase inversions of the magnetic fieldof the cable and acting on receiving antennas located underneath thefloor of the locomotive. It is characterized by the fact that itcomprises three aligned receiving antennas located one after the otherin the longitudinal direction of the track, each antenna being connectedto a band-pass filter, three phase detectors each having two inputsconnected to the outputs of two of the above band-pass filters inaccordance with the three possible different possibilities, such phasedetectors being arranged to deliver an output signal only when theirinput voltages are in phase opposition, a logic circuit for detectingthe direction of travel of the train having three inputs connectedrespectively to the outputs of the three phase detectors, an invertorcircuit for eventually 'permuting two of the phase detector outputs,corresponding to two adjacent antennas, such logic circuit for detectingthe direction of travel of the train having two outputs for deliveringrespectively counting and deduction signals to a circuit for summing thenumber of marking points.

In accordance with another characteristic of the invention, the devicecomprises two threshold level detectors connected respectively to thetwo opposite antennas through band-pass filters and having outputsconnected each through the intermediate of a low-pass filter to a secondlogic circuit for detecting the normal direction of travel of the train.The output of the last-mentioned logic circuit operates theabove-mentioned inverter circuit in a direction or the other inaccordance with the direction of travel of the train on the tracks atthe time of crossing the sector defined by the cable, means beingprovided to store the state of such last-mentioned logic circuit duringthe full travel of the train in the sector under consideration.

The invention will now be disclosed with reference to the followingdescription and to the attached drawings which illustrate an example ofan embodiment of the invention in which:

FIG. 1 illustrates a railway track along the path of which is disposed acable and three detecting antennas;

FIG. 2 illustrates a device for counting the marking points, that is themeasure of the distance travelled by the train; and

FIG. 3 illustrates the waveforms of the variables a, b, and c of FIG. 2as the function of the distance travelled by the train.

In FIG. 1, there is shown a railway track made of two rails R, and Rbetween which is disposed a loop formed by cable K and fed from acentral location by alternating signals originating from a generator G.Cable K has periodic marking points such as P P P The marking points PP, are simple crossings while marking point P is a transposition of thetwo sides of the cable. In any case, it may be seen in FIG. I that atthe crossing of these marking points, the current in the active part ofthe cable undergoes a phase inversion of The device for counting themarking points, that is the measure of the distance travelled by atrain, is illustrated in FIG. 2. It comprises three antennas X, Y, Z,located underneath the floor of a locomotive in the order indicated inFIG. I where the arrow indicates the normal direction of travel of thetrain on the tracks. The antennas are connected respectively toband-pass filters F F F whose output signals, which may be designated1:, y, z respectively, are applied two-by-two to phase detector circuitsDP,, DP DP, which provide at their outputs a logic signal representing astate 1 when their two input signals have a phase difference of 180. Anexample of such detectors is illustrated in Belgian Pat. No. 720,173filed Aug. 30, 1968 and entitled Phase Detector, Particularly for Use inMeasuring the Distance Travelled by a Railway Vehicle." The above phasedetecting circuits receive respectively at their inputs the signals xand y, y and z, z and x The output signals of the phase detectors DP DPDI; designated respectively by a, b, and c are applied to a logiccircuit LDM for detecting the direction of travel of the train. Suchlogic circuit LDM energizes a circuit T, which sums the number ofmarking points, counting signals C and deducting signals D. The signalsa and b pass through an inverter circuit I whose function is toeventually permute such signals and whose control will be explained inthe following part of the description.

FIG. 3 illustrates the wave forms, in function of the distance travelledby the train, of variables a, b, and c at the time of crossing a markingpoint P in the normal direction of travel or, which is the same, in theassumption that the crossing P is displaced in the opposite direction,the antennas X, Y and 2 being fixed. When the crossing is located in thevicinity of the antennas, the variable logic c takes the value 1. Thelogic circuit LDM is designed in such a way that, in this case, itprovides a counting signal to the summing circuit T when the variable bhas a value I (between points e: and e, after the variable a has takenthe value 1 (between points e and e,). It provides, on the contrary, adeduction signal when the crossing is located in the vicinity of theantennas (c=l) and there is obtained a=l after having obtained b=l.

It happens sometimes that the train must travel on the tracks with thelocomotive directed in such a way that the antennas cross the markingpoints in the inverse successive order Z, Y, X. In this case, thecrossings must be positively counted and they must be deducted only whenthe train goes backward. The apparatus is, for this purpose, equippedwith a logic circuit LDC for detecting the normal direction of travel ofthe train. The input variables of the last-mentioned circuit areprovided by two threshold detectors DN and DN to the input of which areapplied respectively the output signals provided by the oppositeantennas X and Z after passing through the band filters F and F Thelast-mentioned detectors are sensible to the input signals only whenthese signals exceed a predetermined threshold. They are equipped, attheir output, with low-pass filters f and F and they provide to logiccircuit LDC a variable logic having a state 1 when their input signalexceeds the threshold level which has been assigned to them. The circuitLDC is designed in such a way that when the variable input logicoriginating from DN takes the state 1 before the one originating from DNtakes the same state, its output has the state 0. The output of circuitLDC takes the state 1 in the situation corresponding to the inversesuccession of input variables in which case it causes the operation ofcircuit inverter l which permits the variables a and b. Thisconsequently, establishes a correct count. The circuit LDC is arrangedin such a way that the state acquired and the input of a defined sectorby the cable is stored during all the travel of the train in suchsector.

The different circuits used in the above-disclosed device and notdescribed in detail may be realized in various ways and differentembodiments may be designed without departing from the scope of thepresent invention.

We claim:

1. In a centralized train control system wherein a cable forming a loopis located between two rails of a track and fed by alternating currentsand wherein said cable has crossings therein or other marking pointsdefining periodic phase inversions of the magnetic field of the cable,which marking points are counted aboard the locomotive of a train inorder to provide an indication of the distance traveled by thelocomotive in the zone defined by the cable, a device for deducting fromthe marking points encountered in the normal direction of travel thoseencountered when going backward, comprising three antennas locatedunderneath the floor of the locomotive and following each other in thedirection of the track, means for comparing two-by-two the phases of thevoltages induced by the cable in the different antennas at the passageof a marking point and for delivering a logic output signal having thevalue 1 when the two compared phases are in opposition, means fordetecting the order of succession of said logic signals and fordelivering a counting signal or a deduction signal depending upon saidorder of succession, and means for summing said counting and deductionsignals with their appropriate signs.

2. A device according to claim 1, wherein the locomotive has front andrear cabins which may be alternatively placed ahead of the train therebyreversing the order of succession of the signals delivered by theantennas, and further comprising means for detecting which one of thetwo extreme antennas is ahead of the train at the entry of thelocomotive in the zone defined by the cable, means responsive to saiddetecting means for storing the state acquired by the antennas at theentry of the zone defined by the cable, and means responsive to saiddetecting means for inverting or not two of said logic input signalsdepending upon the order of succession of the signals delivered by thetwo extreme antennas at the passage of a marking point so as to obtain acorrect counting depending on which one of the two driving cabins of thelocomotive is ahead of the train.

1. In a centralized train control system wherein a cable forming a loopis located between two rails of a track and fed by alternating currentsand wherein said cable has crossings therein or other marking pointsdefining periodic phase inversions of the magnetic field of the cable,which marking points are counted aboard the locomotive of a train inorder to provide an indication of the distance traveled by thelocomotive in the zone defined by the cable, a device for deducting fromthe marking points encountered in the normal direction of travel thoseencountered when going backward, comprising three antennas locatedunderneath the floor of the locomotive and following each other in thedirection of the track, means for comparing two-bytwo the phases of thevoltages induced by the cable in the different antennas at the passageof a marking point and for delivering a logic output signal having thevalue 1 when the two compared phases are in opposition, means fordetecting the order of succession of said logic signals and fordelivering a counting signal or a deduction signal depending upon saidorder of succession, and means for summing said counting and deductionsignals with their appropriate signs.
 2. A device according to claim 1,wherein the locomotive has front and rear cabins which may bealternatively placed ahead of the train thereby reversing the order ofsuccession of the signals delivered by the antennas, and furthercomprising means for detecting which one of the two extreme antennas isahead of the train at the entry of the locomotive in the zone defined bythe cable, means responsive to said detecting means for storing thestate acquired by the antennas at the entry of the zone defined by thecable, and means responsive to said detecting means for inverting or nottwo of said logic input signals depending upon the order of successionof the signals delivered by the two extreme antennas at the passage of amarking point so as to obtain a correct counting depending on which oneof the two driving cabins of the locomotive is ahead of the train.